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TN_EE-BA-e-2020
2.1 Explanation of the key symbols
Switching on/off
Calibration Sound-
speed
Background lighting
On/ Off
Enter key
Button for
Zero-
position
Plus;
scan mode
On/ Off
Button for
Changing the units
Minus;
pulse-echo switch
u. Echo-Echo Mode
Save data o.
delete
3.
Preparation for commissioning
3.1 Selection of the sound generator
With this instrument a wide range of materials can be measured, from various metals
to glass and plastics. For these different types of materials, different sounders, i.e. US
measuring heads, are required. The correct transducer is crucial for a reliable
measurement result. The following sections explain the important characteristics of the
transducers and what should be considered when selecting a transducer for a specific
test object.
In general terms, the best transducer for a test object should send sufficient ultrasonic
energy into the material to be measured so that a strong, stable echo arrives at the
instrument. Certain factors influence the strength of the ultrasound as it is transmitted.
These can be read in the following:
The initial signal strength: The stronger a signal is from the beginning, the stronger the
returning echo will be. The initial signal strength is mainly a factor of the size of the
ultrasonic emitter in the transducer. A strong emitting surface will emit more energy
into the material than a weak one. Consequently, a so-called "1/2 inch" US probe will
emit a stronger signal than a "1/4 inch" US probe.
Absorption and scattering: When the ultrasound passes through any material, it is
partially absorbed. In materials with a granular structure, the sound waves scatter. Both
of these influences reduce the strength of the sound waves and thus the ability of the
device to detect or record the returning echo. Sound waves with higher frequencies
are more "swallowed" than those with lower frequencies.
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